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/*
* btrfs-util.c
*
* Copyright (C) 2014 SUSE. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* Some parts of this taken from btrfs-progs, which is also GPLv2
*/
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/statfs.h>
#include <sys/ioctl.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
#include <linux/magic.h>
#include <linux/btrfs.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "btrfs-util.h"
#include "debug.h"
/* For some reason linux/btrfs.h doesn't define this. */
#define BTRFS_FIRST_FREE_OBJECTID 256ULL
/*
* For a given:
* - file or directory return the containing tree root id
* - subvolume return its own tree id
* - BTRFS_EMPTY_SUBVOL_DIR_OBJECTID (directory with ino == 2) the result is
* undefined and function returns -1
*/
int lookup_btrfs_subvolid(int fd, uint64_t *subvolid)
{
int ret;
struct btrfs_ioctl_ino_lookup_args args;
memset(&args, 0, sizeof(args));
args.objectid = BTRFS_FIRST_FREE_OBJECTID;
ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &args);
if (ret)
return errno;
*subvolid = args.treeid;
return 0;
}
static uint64_t get_btrfs_fsid(fsid_t in_statfs_fsid, uint64_t subvolid,
fsid_t *out_fsid)
{
int *old_fsid = (int *)&in_statfs_fsid;
int tmp[2];
int *fsid = tmp;
uint64_t ret;
if (out_fsid)
fsid = (int *)out_fsid;
/*
* fsid_t is represented as array of 2 ints.
*
* For fsid, btrfs xors different portions of the fs uuid into
* each component of the fsid array. It then masks in the
* subvolume root objectid.
*
* We can reverse the masking to get a unique identifier for
* this filesystem.
*/
fsid[0] = old_fsid[0] ^ (subvolid >> 32);
fsid[1] = old_fsid[1] ^ subvolid;
ret = (uint64_t)fsid[0] & ((1ULL << 32) - 1);
ret |=(uint64_t)fsid[1] << 32;
return ret;
}
/*
* Figure out if we're btrfs. If we are, get the fsid. Otherwise
* return 0 in *ret_fsid.
*/
int check_btrfs_get_fsid(char *name, struct stat *st, uint64_t *ret_fsid)
{
struct statfs fs;
int ret, fd;
uint64_t subvol;
*ret_fsid = 0;
ret = statfs(name, &fs);
if (ret) {
ret = errno;
goto out;
}
if (fs.f_type != BTRFS_SUPER_MAGIC)
return 0;
fd = open(name, O_RDONLY);
if (fd == -1) {
ret = errno;
goto out;
}
ret = lookup_btrfs_subvolid(fd, &subvol);
if (ret)
ret = errno;
*ret_fsid = get_btrfs_fsid(fs.f_fsid, subvol, NULL);
close(fd);
out:
return ret;
}
#ifdef BTRFS_UTIL_TEST
static int get_fsid(int fd, fsid_t *ret_fsid)
{
int ret;
struct statfs fs;
fsid_t fsid;
uint64_t subvolid;
int *f;
ret = fstatfs(fd, &fs);
if (ret)
return errno;
if (fs.f_type == BTRFS_SUPER_MAGIC) {
uint64_t id;
ret = lookup_btrfs_subvolid(fd, &subvolid);
if (ret)
return ret;
id = get_btrfs_fsid(fs.f_fsid, subvolid, &fsid);
f = (int *)&fs.f_fsid;
// printf("btrfs fsid: %x.%x (%"PRIx64", subvol: %llu\n",
// f[1], f[0], id, (unsigned long long)subvolid);
} else {
fsid = fs.f_fsid;
}
*ret_fsid = fsid;
return 0;
}
int main(int argc, char **argv)
{
int i, ret, fd;
char *filename;
fsid_t fsid;
int *f;
if (argc < 2) {
printf("Missing arguments\n");
return 1;
}
for (i = 1; i < argc; i++) {
filename = argv[i];
fd = open(filename, O_RDONLY);
if (fd == -1) {
perror("opening file");
continue;
}
ret = get_fsid(fd, &fsid);
if (ret) {
fprintf(stderr, "ERROR: %d\n", ret);
return ret;
}
f = (int *)&fsid;
printf("%s: fsid: %x.%x\n", filename, f[1], f[0]);
close(fd);
}
return 0;
}
#endif /* BTRFS_UTIL_TEST */
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